Major Works

Cosmic Rays Laboratory

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Félix Candela’s fourth thin concrete shell built, the Cosmic Rays Laboratory, was the first of his stunning hyperbolic paraboloids, the form of his most famous structures. The laboratory is the thinnest major structure ever built. At only 5/8 inch, it displays a daring solution to the problem of building a structure with an interior that permits the measurement of cosmic radiation. Candela was able to construct a lightweight shell that expresses thinness by its cantilevered edges. Designed to house two small laboratories the laboratory is located where cosmic rays had first been investigated on the UNAM campus, by the Mexican physicist Sandoval Vallarta.1 The head of campus construction, Carlos Lazo, sought out Candela for help in building this permanent structure with a roof no more than 5/8 inch thick.

The original form chosen by the collaborating architect was a barrel shell which Candela redesigned to be a hyperbolic paraboloid because he believed that its extreme thinness would require the extra stiffening offered by this form. He also changed the supports to their present form and added the concrete screens on the ends of the shell. The upward curvature of the cantilevered ends of the shell enhances its visual lightness. However, Candela doubted if the shell would be strong enough, so he added three stiffening arches not visible from the outside. As the construction was about to start, UNAM officials approached Candela and asked to see his calculations, but there were none. Instead, Candela simply wrote a few pages explaining why the shell would stand; this satisfied the officials.

The erection of the laboratory was much less complicated than its double curvature implies because the hyperbolic paraboloid can be formed by straight boards crossing at a 60-degree angles. By layering these “straight-line generators,” Candela could easily build the formwork and then proceed to cast the concrete. The structure still stands in fine condition on the UNAM campus. However, the mystery of cosmic rays has been replaced by the mastery of a board game, as the lab is gone and the building is now the home of the chess club.

It is remarkable that Candela was able to build a shell so thin at such an early point in his career. However, after his experiences building other hypars, Candela realized that he made a mistake with the Cosmic Rays Laboratory design. The form was so efficient that he did not need the stiffening arches. The structure one sees from the outside is also not completely honest. While the cantilevered edges attempt to express the thinness of the shell, the actual size of the shell at its thinnest is hidden from observers. In addition, there is no evidence of the existence of the interior stiffening arches. Whereas Candela’s future works show more play and exploration of the hypar form, the Cosmic Rays shell is merely two simple hypar saddles abutting in the center. Yet the shell is remarkable for its incredible thinness, and its role as a springboard for Candela to pursue and experiment with hyperbolic paraboloids.